Evaporative media systems, for example direct evaporative coolers, are frequently used in commercial and industrial HVAC systems, including applications for data centers and power plant turbine inlet cooling. Evaporative media systems consume less energy than conventional cooling equipment and are increasingly being used to supplement and occasionally replace conventional cooling equipment. In operation, evaporative media systems use the enthalpy of vaporization of water as a means to cool and humidify air. Typically, this is accomplished by flowing air directly through a media wetted with water. As air passes through the wetted media, water evaporates by taking energy from the air to vaporize the water. Accordingly, the air temperature exiting the wetted media is reduced and the humidity is increased while the energy or enthalpy of the exiting air remains the same as the entering air. This type of a process is often referred to as adiabatic cooling.
Evaporative media systems typically use a water pump to transfer water in a tank below the media to the top of the media. The water flows down through the media where a small portion of the water evaporates and a relatively larger portion drains out the media bottom into the tank below. The water continues to be recirculated using the water pump, or re-circulation pump, with make-up water added to replace the evaporated water. Tank water is periodically drained and replaced with additional make-up water to control tank water concentration and minimize scale fouling, biological fouling and corrosion.
The air flowing through an evaporative media system allows for the introduction of algae. Additionally, the continuously wet environment may allow that algae to propagate. If measures are not taken, algae can fowl the media and contaminate the air being conditioned by the system. To prevent the continuous growth of algae, it is common practice to allow the media to completely dry out at least once in any given 24 hour period in a dry out cycle. However, by requiring the media in an evaporative media system to completely dry out, the system is necessarily inactive and no longer flowing water. Thus, the desired cooling and humidification effects are temporarily lost during the dry out cycle. The length of a dry out cycle, and subsequent delay in desired output, is dependent on incoming air conditions. The dry out cycle is often a scheduled event that occurs regardless of past system output. Improvements are desired.